Human toes rigged not deforming correctly
The easyest way to do what you described is probebly to rig each of the tose seprat and fix them separat.

If you rig the tose as one bone they will be deformed as one object and will probebly create a new problem if you fix one.
The deformation is done lineal and you whold need to make a exponetial deformation to make it work. You could cheat and play with the weights and make it god enoth but it will be limeted.